A Level Biology Edexcel: Topic 5 - 8
This flashcard set covers the whole of topics 5- 8 by spec point. This is mainly for memorization of the key aspects in each topic. It is recommended to learn these facts well before attempting practice question as you will have a general idea of possible answers and questions that could be asked. Hope it helps :)
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A Level Biology Edexcel: Topic 5 - 8 - Leaderboard
A Level Biology Edexcel: Topic 5 - 8 - Details
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| Outline the light dependent reaction | Light energy is absorbed by the chlorophyll in PSII causing electrons to be excited and boosted to a higher energy level the electrons are picked up by an electron acceptor the electrons move down an ETC through a series of redox reactions to PSI as the electrons move down the ETC, they release energy which is used for chemiosmosis The electrons lost in PSII are replaced by the photolysis of water oxygen is given off as a waste gas and H+ ions and electrons are used to form NADPH and ATP |
| GPP | Gross primary productivity the energy transferred to primary consumers |
| Ecosystem | All the organisms living in a particular area, known as the community, as well as all the non-living elements of that particular environment |
| Community | All of the populations of all the organisms living in a particular habitat at a particular time |
| Where does the light dependent reaction occur? | Happens in the thylakoid membrane |
| Population | All the organisms of a particular species living in a particular habitat at a particular time |
| Outline chemiosmosis | Hydrogen ions from the stroma are actively pumped into the thylakoid lumen energy from the electron transfer chain is used to do this this forms an electrochemical gradient because of the difference in concentration of H+ ions the H+ ions in the lumen flow through ATP synthase by facilitated diffusion forming ATP and NADPH which will be used in the light independent reaction |
| Habitat | The place where an organism lives |
| Outline the Light independent reaction | RUBP and CO2 combine to form a 6 carbon intermediate that immediately divides to form GP (3C) the RUBP + CO2 reaction is catalysed by rubisco NADPH and ATP are then used to catalyse the conversion of GP into GALP (3C) some molecules of GALP combine to form glucose (6C) whilst the rest are used to regenerate the RUBP using ATP |
| Photosynthesis | The biological process that occurs in plants which convert carbon dioxide and water into glucose and oxygen in the presence of sunlight |
| Light independent reaction | Also known as the Calvin cycle occurs in the stroma of the chloroplast uses CO2, NADPH and ATP products are glucose, NADP+ and ADP+Pi has three stages: carbon fixation, reduction and regeneration |
| Two stages involved in photosynthesis | Light dependent reaction and Light independent reaction (Calvin Cycle) |
| Structures of the chloroplast | Thylakoid stroma lamellae grana/granum inner membrane outer membrane intermembrane space |
| Structures of the thylakoid | Thylakoid lumen thylakoid membrane photosystems I and II chlorophyll ATP synthase electron carrier proteins |
| Photophosphorylation | The conversion of ADP into ATP using energy from sunlight |
| Process of photolysis | Energy from sunlight is used to break the bonds between the hydrogen atoms and the oxygen atom in a water molecule hydrogen is then further split into H+ ion and electrons |
| Ecosystem | All the living organisms in a particular area, known as the community and all the non-living elements of that particular environment |
| Community | All of the populations of all the organisms living in a particular habitat at a particular time |
| Population | All of the organisms of a particular species living in a particular habitat at a particular time |
| Habitat | The place where an organism lives |
| Succession | The change in species inhabiting an area over time |
| Primary succession | Occurs when an area previously devoid of life is first colonised by communities of organisms |
| Secondary succession | Occurs with existing soil that is clear of vegetation |
| Abiotic | Non living factors of a habitat |
| Biotic | Living factors of a habitat |
| Niche | The role of an organisms in its habitat |
| Niche concept | States that only one organism can occupy each niche in a given habitat at a given time if two or more species have a niche that overlaps, the best adapted will out-compete the others to survive and reproduce |
| What is the distribution and abundance of organisms in a habitat controlled by? | The biotic and abiotic factors in the habitat |
| What does a niche consist of? | Biotic and abiotic interactions with the environment |
| What does species distribution and abundance depend on? | The number and type of ecological niches available within the habitat |
| What is succession brought about by? | It is brought about by changes to the environment made by organisms colonising it themselves |
| Humus | The organic component of soil |
| What is NPP? | Net primary productivity the difference between energy fixed by autotrophs and their respiration |
| What is GPP? | Gross primary productivity the energy transferred to primary consumers |
| Equation combining GPP, NPP and respiration | NPP = GPP - R |
| Define primary productivity | The rate at which energy is converted into organic substances by photosynthetic and chemosynthetic autotrophs |
| Define ecosystem | All the biotic and abiotic factors of a particular area |
| Define community | All of the populations of all the organisms living in a particular habitat at a particular time |
| Define population | All of the organisms of a particular species living in a particular habitat at a particular time |
| Define habitat | The place where an organism lives |
| Define biotic | The living elements of a habitat |
| Define abiotic | The non-living elements of a habitat |
| What is the distribution and abundance of a habitat controlled by? | Biotic and abiotic factors |
| Define niche | The particular role of a species in a habitat |
| What does a niche consist of? | Biotic and abiotic interactions with the environment |
| What does species distribution and abundance in a habitat depend on? | The number and type of ecological niches available within the habitat |
| What is the niche concept? | States that only one organism can occupy each niche at a given time if two or more species have a niche that overlaps, the best adapted will outcompete the others to survive and reproduce |
| Define succession | The change in species inhabiting an area over time |
| What is succession brought about by? | Changes to the environment made by organisms colonising it by themselves |
| What is primary succession? | Occurs when an area previously devoid of life is first colonised by communities of organisms |
| What secondary succession? | Occurs with existing soil that is clear of vegetation |
| What is humus? | The organic component of soil |
| What are pioneer species? | Species that first colonise an ecosystem they are adapted to survive in harsh conditions they can break down rocks and hold together sands |
| What happens when organisms die? | They are decomposed by microorganisms this adds humus leading to soil formation over time more decomposed organisms adds more minerals to the soil this allows for more varied and complex organisms to survive |
| What is a climax community? | The most productive, self-sustaining and stable community that an environment can support, usually with only one or two species |
| Stages of succession | Pioneer species primary succession secondary succession climax community |
| Calculate efficiency of biomass and energy transfers between tropic levels | % efficiency = (energy from a lower trophic level/energy from a higher trophic level) X 100 |
| Define climate | The average weather conditions over a long period of time |
| Define climate change | The long term shift or change in average weather patterns in a place over time |
| Define anthropogenic | Man made GHG emissions |
| Define weather | The term used to describe daily conditions |
| Define global warming | The gradual increase in the average temperature of the Earth's atmosphere and surface |
| Evidence for climate change | Pollen in peat bogs CO2 emissions and temperature levels records dendrochronology |
| Results of climate change | Reduction in species more flooding, storms and droughts ice caps melting sea levels and temperatures rising |
| What are peat bogs? | Partially decomposed organic matter has anaerobic and acidic conditions that prevent bacteria decomposing the organic matter |
| Pollen in peat bogs | Very resistant to decay they are varied and unique are only produced when the plant is matured their abundance in each layer of the peat bog can be used to analyse climate change their DNA can be analysed to see what conditions the plant they came from grew in |
| CO2 emissions and temperature level records | Temperature level records as far back as 1850 CO2 records can be obtained as far back as 10 - 15 million years ago these are both important factor and contributors to climate change |
| What is dendrochronology? | Study of trees the width of tree rings can be studied to determine climate change |
| The greenhouse gases | CO2, water vapour, methane, N2O they absorb heat energy and reflect it back to the earth |
| What is the greenhouse effect? | The trapping of UV radiation in the Earth's atmosphere and reflecting the heat back down to the Earth's surface |
| Greenhouse effect | The sun emits heat energy through radiation most of the radiation is absorbed by the earth whilst the rest is reflected back into space short wavelength UV radiation passes through the earth's atmosphere and is reflected from the surface the reflected rays are of a longer wavelength (infrared radiation) and are trapped by GHGs this leads to an increase in the temperature of the Earth's surface and atmosphere |
| Why do models for climate change have limitations? | There is not enough knowledge about the initial conditions of the climate system |
| What are the effects of climate change on plants and animals? | Change in distribution of species change in development of organisms change in the life cycles of species |
| How does climate change affect the distribution of species? | Species will have to migrate to cooler places this will cause competition in that area eventually leads to extinction due to lack of food and space |
| How does climate change affect species development? | The sex of some species is determined by the temperature an increase in temperature may effect the sex ratio of these species this leads to extinction because the sex ratio is imbalanced |
| How does climate change affect life cycles? | Increased temperature increases enzyme activity so more enzyme-substrate complexes are formed increasing the rate of reaction however at temperatures above the optimum rate of reaction decreases as enzymes denature |
| Evolution | The change in allele frequency of a population over time as a result of natural selection |
| Natural selection | The process where organisms are better adapted to an environment to survive and reproduce advantageous alleles are passed down to the offspring leads to evolution |
| Gene mutation | Change in bases sequence on DNA could cause a change in amino acid this may lead to a different protein structure |
| How can evolution come about through gene mutation and natural selection? | Selection pressure changes alleles change in some of the species the allele is advantageous for them to survive in the environment they can pass down the allele to their offspring those without the allele die as time goes on the frequency of the advantageous allele increase in the species |
| Selection pressure | External agents which affect an organism's ability to survive in a given environment |
| Speciation | The evolution of new species from existing ones occurs when there is a lack of gene flow between two populations of species resulting in each population evolving differently |
| Gene flow | The transfer of alleles between organisms |
| Two types of speciation | Allopatric and sympatric |
| Allopatric speciation | Population is isolated by geographical features prevents them from breeding they are reproductively isolated |
| Reproductive isolation | The inability of a species to breed successfully with related species due to geographical, behavioural, physiological or genetic barriers/differences |
| Sympatric speciation | Same species found in the same location/habitat evolve differently due to other factors so can no longer produce fertile offspring |
| What can sympatric speciation occur from? | Ecological isolation temporal isolation behavioural isolation physical incompatibility hybrid inviability hybrid sterility |
| Ecological isolation | Species occupy different areas of the habitat |
| Temporal isolation | Species reproduce at different times but within the same area |
| Behavioural isolation | Species do not respond to the courtship behaviour but are found in the same area |
| Physical incompatibility | Species can co-exist but physical reasons stop them from mating |
| Hybrid inviability | Offspring is produced but they don't survive |
| Hybrid sterility | Offspring can survive to the reproductive age but do not reproduce |
| Investigate photosynthesis using isolated chloroplasts (the Hill Reaction) | Grind leaves with ice cold sucrose solution in a mortar and pestle strain the liquid into a cooled centrifuge tube and centrifuge for 5 mins at medium speed pour the supernatant into another cooled centrifuge tube and centrifuge for 10 mins at high speed decant and discard the supernatant add ice cold sucrose solution and ice cold pH 7 buffer solution to the left over sediment and mix gently pour equal volumes of the mixture into test tubes A, B and C, also add the same volume of DCPIP to test tube D only boil tube C over a Bunsen burner then cool it under a tap add some DCPIP to test tubes A, B and C leave tubes A, C and D under a lamp and place B in a cupboard observe until all the colour in tube A has disappeared |
| What does the Hill Reaction prove? | Isolated chloroplasts can still produce oxygen in the presence of light providing evidence for the light dependent reaction |
| Investigate the effect of temperature on the initial rate of an enzyme-catalysed reaction | 5 different temperatures of water baths between 10°C - 50°C put some hydrogen peroxide into a conical flask put the conical flask in the water bath to acclimatise for 2 minutes add some yeast to the conical flask and immediately bung up the conical flask take readings from the gas syringe every 30 seconds for about 3 mins repeat this at each temperature 3 times |
| Q10 | The temperature coefficient measures the rate of change of a reaction when the temperature is increased by 10°C Q10 = rate at higher temperature / rate at lower temperature |
| Investigate the effect of temperature on brine shrimp | 5 different temperatures of water baths between 10°C -30°C add some sea salt to the water in a beaker and stir till it has all dissolved pour out some eggs onto some paper dip some paper in the saltwater to pick up about 40 eggs re dip the wet paper with attached eggs into the saltwater solution place each beaker into the water baths for 24 hours or more count how many eggs hatched out of the 40 eggs repeat to get means |
| How do you determine the time of death of a mammal? | Examine the extent of decomposition, stage of succession, forensic entomology, body temperature and the degree of muscle contraction |